Field of Invention
The present invention relates to the field of high-temperature protection for metals, and more particularly to a surface alloy coating composite material used for a high temperature resistant materials and a manufacturing method thereof.
Description of Related Arts
The variety of turbines, such as the steam turbine and gas turbine, the heat-side components thereof are typically operated in harsh environments. These harsh environments may cause erosion, high temperature oxidation, hot corrosion damage, and combinations thereof. In addition, the thermal fatigue can cause the components to crack, and after a long run, the components may be further break.
In order to pursue higher power generation efficiency and reduce carbon emission, the operating temperature of the turbine needs to be continually improved. But increasing the operating temperature, the heat resistance of the hot-stage components has to be improved. Thus, a high-temperature alloy component needs to be provided with an anti-oxidation and corrosion resistant coating, thermal diffusion coating or thermal barrier coating. The thermal barrier coatings for high-temperature alloy hot-stage components include metal bonding layers and ceramic insulation layers. U.S. Pat. No. 6,610,420 reported a method for preparing a thermal barrier coating, they firstly coat an anti-oxidation layer containing components A and B on the surface of the high-temperature alloy component by hot spraying, then hot spray a bonding layer containing component C, and finally hot spray a thermal insulation layer made of ceramic material, wherein the components B and C are NiCrAlY alloy, the component A is NiSiCr alloy.
U.S. Pat. No. 5,942,334 reports a MCrAlY anti-oxidation alloy, which can be used for enhancing the binding force of the ceramic layer and preventing the base matrix high-temperature alloy being oxidized. Many ceramic materials are used as the ceramic layer, in particular yttrium oxide or magnesium oxide or other oxide stabilized zirconia. These particular materials are widely used, for they can be coated by plasma spraying, flame spraying and vapor deposition method, and they can still reduce heat radiation. For achieving the purpose of thermal insulation, the thermal barrier coatings must have low thermal conductivity, good combination with the substrate, and can withstand thermal cycling without peeling. A thermal expansion coefficient matching between the coating material and the substrate material is required for anti-thermal cycling peeling. Therefore, the manufacturing method for the thermal barrier coating is usually applying firstly a metal bonding layer on the high-temperature alloy substrate and then applying a thermal insulation layer.
U.S. Pat. Nos. 6,475,647 B2 and 6,475,647B2 report methods for preparing a dense NiCrAlY coating having an anti-coking property. In these methods, the raw material powder for the NiCrAlY coating is heated by plasma transferred arc and blown to the components by argon gas, which is used for preventing the raw powder being oxidized. During the coating process, by controlling the process parameters, molten pool is formed in the surface of the components, the coating having a desired thickness is finally formed in the components. The substrate alloy is melt, which results a diluted coating such that the actual composition of the coating is deviated from the composition of the raw materials, and a transition zone is located between the substrate and the coating, which contains some of the carbides and nitrides dispersed therein. These compounds are generated by carbon and nitrogen high-temperature diffusion in an ethylene furnace and significantly reduce the peeling tendency of the coating. U.S. Patent No. U.S. 2009/0098286A1 reports a method for hot spraying a thermal barrier coating on the heat-side components of a gas turbine.
In a gas turbine, the conventional protective coatings for nickel-based high-temperature alloys can be divided into two types: thermal diffusion aluminide coating and physical vapor deposition or thermal spraying NiCrAlY coating. These coatings have good compatibility with high-temperature alloys. But when the effective component of Al in the coating is lost due to forming of an oxide film and inter-diffusion between the coating and the substrate, the coating will lose effectiveness. In contrast, the inert oxide coating will not lose effectiveness because of the loss of the effective component, but the inert oxide coating is easier to be peeled and failed than the aluminide coating and the NiCrAlY coating, which is caused from the thermal expansion coefficient mismatching between the coating and the substrate.
Under an appropriate condition, enamel-ceramic coating have a good bonding capability with many metals and alloys, which is an important reason that such coatings are widely used. By controlling the crystallization preparation of the base glass, the enamel-ceramic material not only retains ease of use of the enamel coating, and combines some of the special advantages of the ceramic crystals. The enamel-ceramic material has better mechanical strength and heat resistance than the original enamel, and the thermal expansion coefficient of the enamel-ceramic material can be adjusted to match the substrate. It has been proved that SiO2—Al2O3—ZnO—CaO-based enamel coating has a good protection for intermetallic compound. Alumina-enamel composite coating was also found to be adapted for nickel-based alloys, which has long-term resistance against high temperature oxidation at 1000° C. and hot corrosion at 900° C. However, due to the higher intrinsic brittleness and cracking sensitivity of the enamel material, the enamel or alumina-enamel composite material as a coating material has a weakness, which is weak-resistance for peeling under thermal cycling conditions.